This invention relates to printed circuit technology and more specifically to plug-in circuit cards, e.g. memory cards, for computers.
With rapidly advancing computer technology it is now conventional for computers, especially personal computers, to allow customizing, i.e. upgrades, enhancements, additions etc., of new accessories or system software improvements by simply installing new printed circuit cards in an existing computer. Such options include expansion boards, single in-line memory modules (SIMM), external peripherals for multimedia, modems, printers, fax, video DRAM chips, system processor upgrades, etc. This same capacity to use plug-in expansion boards or cards also allows easy assembly and repair of basic computer components that are typically part of the computer when purchased, e.g. hard disks, CD-ROM readers and diskette drives.
The printed circuit plug-in boards or cards, hereinafter referred to as printed circuit cards (PC cards), are printed circuit boards carrying many integrated circuit packages. To fit the typical computer housing the cards are rectangular in shape with a relatively long side along which is disposed at least one row of I/O contacts.
The computer housing is provided with plug-in sites, typically referred to as PCI or ISA slots, for installing repair or expansion PC cards. These sites have rectangular slots, with channels typically along two or three sides, for mounting the cards. The slots have at least one socket with a linear array of contacts. The socket portion of the slot is typically positioned to engage the I/O contacts along the long dimension of the card, and is situated along the floor of the computer housing for a vertical card installation, or along a sidewall or partition in the computer for a horizontal card installation. The cards have a linear array of contacts that corresponds to the linear array of the socket so that when the cards are installed the contacts of the cards mate with, or plug into, the linear array of contacts in the socket. The size and spacing of the contacts on both the socket and the cards conform to industry standards.
The manufacture of the expansion or repair cards is typically a batch process in which multiples of cards are processed as a batch on a common processing panel. At a late stage in the manufacturing sequence, typically after the component packages are inserted (or placed) and soldered, the individual cards are singulated. The singulation step involves cutting the common processing panel into single PC cards. The individual PC cards are then subjected to final testing. In the manufacture of many high performance PC boards the electrical testing may include a burn-in test.
Electrical testing of these high performance PC cards is preferably carried out using an insertion type test apparatus. The contacts on the test apparatus may be designed for conventional plug insertion, but are more likely to be zero force insertion contacts. For the purpose of this description, these types of testers are termed insertion testers or insertion test apparatus. Insertion type testers require direct access to the row of I/O contact pads by a corresponding row of test contact pads in the insertion tester. An insertion type test apparatus requires the contacts being accessed to be situated at the edge of the card where they can be inserted into the mating array of test contacts. In a typical common processing panel, many or most of the electrical contacts that require addressing for the test are not situated at the edge of the panel and these contacts are not suitable for testing with an insertion type test apparatus. Therefore, it is the common practice in the manufacture of PC cards to singulate the multiple PC cards from the common process panel for insertion testing. It is evident that singulating the PC cards involves considerable handling, leading to both higher costs of manufacture, and increased defects and failures. It would be desirable to test the PC cards while still integrated as a common processing panel so that final packaging and testing can be performed as a batch process.
While multiple cards on a common test panel can be tested using a xe2x80x9cbed of nailsxe2x80x9d tester, reliable electrical testing requires direct electrical contact over a significant area of the I/O contact pad. Moreover, in testing high reliability IC devices it is desirable to use burn-in test procedures. Bed of nails testers are not useful under burn-in conditions because the contact area between the nails and the pads being probed is very small and the electrical resistance varies widely under the severe conditions of the burn-in test. Reliable burn-in tests require direct electrical contact with an insertion type tester so that electrical contact occurs over a substantial part of the I/O pad.
The ability to process and test PC cards as a batch, i.e. as a single integrated panel, is especially attractive in processes where final packaging can also be completed in a batch operation. Final packaging of some devices in current manufacture, e.g. certain SIMM devices with flip-chip mounting, involves epoxy underfill of the flip-chip substrates. After the application of the epoxy underfill it is difficult and in some cases impractical to remove a defective device for repair or replacement. Accordingly it is important to complete testing, including burn-in if necessary, prior to application of the epoxy underfill. Since it is considerably more convenient and cost effective to apply the underfill in a batch process it is evident from this standpoint as well as that already discussed that a testing procedure that allows both testing and final packaging to be performed in a common batch operation would be an important advance in the art.
We have developed a batch testing technique for PC cards in which multiple PC cards are processed as a common processing panel, and the processing panel is subjected to electrical testing, including burn-in testing if desired. The PC cards thereafter undergo further assembly and packaging steps as necessary while still integrated as a single processing panel. The enabling feature for this advance is the provision of rows of additional test contacts along at least one of the short edges of the card, or on the processing panel alongside at least one of the short edges of the card, so that the rows of test contacts are accessible to contact pads in a test apparatus. This allows electrical contacts to every component on the multiple card sites to be inserted into an insertion type tester thus enabling reliable and robust electrical testing, including burn-in testing if required. The added row or rows of test contacts can be eliminated in the singulation step.